Modern aircraft, in particular transport airplanes, comprise an automatic piloting system enabling a pilot of the aircraft to select at least one guidance mode which is implemented automatically by the automatic piloting system when the automatic piloting is engaged. For example, in a cruising flight phase of the aircraft, a guidance mode may consist in following a previously defined flight plan. In a take-off phase of the aircraft, a guidance mode may consist in keeping the wings of the aircraft flat when rolling on a take-off runway: when the automatic piloting is engaged, the automatic piloting system automatically controls the roll angle of the aircraft so as to keep the wings of the aircraft flat. Another guidance mode relates to an automatic rotation of the aircraft upon take-off: when the automatic piloting is engaged, the automatic piloting system automatically controls the aircraft in such a way as to keep it on the ground while travelling to take-off until it reaches a predefined rotation speed Vr, then it controls the rotation of the aircraft by controlling the pitch angle. These two guidance modes can be combined during the take-off phase of the aircraft.
To activate the automatic piloting of the aircraft, the pilot has to select at least one guidance mode, either by buttons situated on a control panel, or by selecting this guidance mode in dedicated screen pages, then he or she has to engage the automatic piloting by pressing on a button generally situated on a control panel of FCU (Flight Control Unit) type situated between display screens of the cockpit and the windshield. In some situations, it may be necessary for a pilot of the aircraft to deactivate the automatic piloting to switch to a manual piloting mode. These situations may, for example, correspond to avoidance maneuvers performed in manual piloting mode. Thus, in cruising flight phase, it may be necessary to perform an avoidance maneuver to avoid a weather disturbance. In take-off phase, it may be necessary to perform an avoidance maneuver, for example to avoid birds in proximity to the take-off runway. Conventionally, the pilot deactivates the automatic piloting of the aircraft by pressing on a button situated on the control wheel, the control column or the mini-stick of the aircraft, then he or she manually controls the aircraft by the control wheel, the control column of the mini-stick (depending on the type of aircraft). If, after this manual control of the aircraft, the pilot wants to re-engage the automatic piloting, he or she must again press on the button situated on the FCU. Upon taking the situation of the FCU in the cockpit into account, the pilot has to lean forward to press on this button. This may be stressful for the pilot in a flight phase such as take-off, during which the pilot has to be particularly attentive to numerous events. He or she may then prefer to continue the take-off in manual piloting mode after having performed the avoidance maneuver, rather than re-engage the automatic piloting to continue the take-off. In cruising phase, modern aircraft are particularly stable even in the absence of control from the pilot on the control column or the mini-stick, when the aircraft is in manual piloting mode. The result thereof is that it is necessary to display clearly visible indicators on the screens of the cockpit to enable the pilot to be aware of the piloting mode engaged (automatic piloting or manual piloting).
When the pilot disengages the automatic piloting by pressing on the button situated on the control wheel, the control column or on the mini-stick, the automatic piloting system of the aircraft may still display a flight director on a screen of the cockpit. This flight director corresponds to the guidance modes previously selected by the pilot. It therefore enables the pilot to control the aircraft in a manner consistent with the automatic piloting which was previously engaged. However, when the pilot disengages the automatic piloting to perform an avoidance maneuver, this avoidance trajectory is not generally consistent with the selected guidance modes. The result thereof is that the flight director is then not useful. The pilot can clear its display, but this has the effect of deselecting the guidance modes. If the pilot wants to re-engage the automatic piloting after having performed the avoidance maneuver, he then has to reselect the desired guidance mode or modes before pressing on the button of the FCU to engage the automatic piloting, which increases his or her workload.